Apple II Power Supply - magic smoke all gone

[D Finnigan]

In a tragic twist of irony, I powered on my Apple II Plus last evening after
a year in storage to test it. Didn't have it on much longer than 25 minutes
or so when I heard a sickening noise. A crinkling sound, then a column of
acrid smoke rose from the rear (switch end) of the power supply. Like a
flash I flipped off the switch and pulled the plug, but I fear the damage is
done.

If you've read up to chapter 2 of The New Apple II User's Guide, or have
looked at the back cover of that book, then you have seen this Apple II
Plus, a fairly early model from spring 1979. And what I presume is its
original power supply is now up in smoke!

Now I'm asking the Apple II community if someone can provide a replacement
supply, can fix this one, or can offer instructions for me to fix it.

I'll be highly appreciative.

[Michael J. Mahon]

Be of good cheer. ;-)

The odds are excellent that the only failure is the mains filter capacitor,
an "X1" type, that is easily replaced. (In fact, you can even run without
it!)

The downside, as you've observed, is the strong, disgusting odor, but that
will slowly dissipate.

You may also have blown the nearby fuse, also easily replaced.

If the X1 capacitor (a box-like affair, about an inch square and 1/4"
thick, mounted on its edge) isn't obviously blown, the problem may be
elsewhere, but first, the most likely thing...
--
-michael - NadaNet 3.1 and AppleCrate II: http://michaeljmahon.com

[D Finnigan]

Michael J. Mahon wrote:
> D Finnigan <dog...@macgui.com> wrote:
>> In a tragic twist of irony, I powered on my Apple II Plus last evening
>> after
>> a year in storage to test it. Didn't have it on much longer than 25
>> minutes
>> or so when I heard a sickening noise. A crinkling sound, then a column of
>> acrid smoke rose from the rear (switch end) of the power supply. Like a
>> flash I flipped off the switch and pulled the plug, but I fear the damage
>> is
>> done.
>>
>> If you've read up to chapter 2 of The New Apple II User's Guide, or have
>> looked at the back cover of that book, then you have seen this Apple II
>> Plus, a fairly early model from spring 1979. And what I presume is its
>> original power supply is now up in smoke!
>>
>> Now I'm asking the Apple II community if someone can provide a
>> replacement
>> supply, can fix this one, or can offer instructions for me to fix it.
>>
>> I'll be highly appreciative.
>
> Be of good cheer. ;-)

I'll do my best. :-p

>
> The odds are excellent that the only failure is the mains filter
> capacitor,
> an "X1" type, that is easily replaced. (In fact, you can even run without
> it!)

My instinct tells me it was a capacitor, just from the sound I heard.

>
> The downside, as you've observed, is the strong, disgusting odor, but that
> will slowly dissipate.

Had to clear the room. :-( Fortunately for me the room where this occurred
is not the one where I lay my head to sleep that night. ;-)

>
> You may also have blown the nearby fuse, also easily replaced.
>
> If the X1 capacitor (a box-like affair, about an inch square and 1/4"
> thick, mounted on its edge) isn't obviously blown, the problem may be
> elsewhere, but first, the most likely thing...
>

Haven't opened this brick yet. I don't even know how it's done. I've heard
or read somewhere that you have to drill out bolts or screws.

I have not applied power or done anything whatsoever with the machine or
supply, other than put it back in the cardboard storage box the next day.


--
]DF$
The Marina IP stack for Apple II--
http://marina.a2hq.com/

[Raymond Wiker]

Do all Apple ][ supplies have main filter capacitors? I have 2 A2M001
supplies (in early Apple ][ computers) that do not seem to have filter
caapacitors (I could well be wrong, though).

[Michael J. Mahon]

I wouldn't be surprised if early supplies didn't have a line filter
capacitor.

[Michael J. Mahon]

To remove the bottom pan, you'll need to drill out about a half-dozen (or
8?) rivets.

It's not hard, but... remember there's stuff on the other side when
drilling, so don't drill IT. ;-)

Often, you needn't drill all the way through, just far enough to pop the
rivet.

[D Finnigan]

Michael J. Mahon wrote:
>
> To remove the bottom pan, you'll need to drill out about a half-dozen (or
> 8?) rivets.
>
> It's not hard, but... remember there's stuff on the other side when
> drilling, so don't drill IT. ;-)
>
> Often, you needn't drill all the way through, just far enough to pop the
> rivet.

Thanks.

And you were right: the power supply still works. :-)

[TomCh]

Coincidentally, I had exactly the same thing happen to my PSU only a month ago! IE. just taken out of >1 year storage, acrid fumes on power on, but PSU continues to work.

It's good to get an understanding of why it still works, and that it's OK to do nothing about it.

[Michael J. Mahon]

Although the supply works fine without the line filter capacitor, there are
two good reasons to replace the failed one: 1) it smells awful, and the
sooner it's out of your Apple the sooner it will stop smelling bad, and 2)
a line filter reduces the vulnerability of the supply to line spikes and it
also reduces noise conducted back to the line.

Then there's the educational aspect of learning how to work on your power
supply. ;-)

[Chris Zuhars]

OK, about "running the PSU without the filter caps" - how exactly is that done? Just de-solder the old cap and run as-is? Or do you have to jumper the leftover holes? I've always been curious.

[Michael J. Mahon]

First, it's not "running the PSU without the filter caps", since each
supply voltage must be filtered by electrolytic caps to remove the HF
ripple.

It's the *line* X1 filter cap that is not necessary for operation. And
since it fails open (well, actually, it shorts, then the AC line "opens" it
with a pop and a stink), nothing actually needs to be done to operate the
supply without it--though it smells better to remove it and it's even
better to replace it.

This capacitor is connected directly across the AC line, so, no, don't
jumper the holes!

[Michael J. Mahon]

newt <drpo...@icloud.com> wrote:

> Hey Micheal!,
>
> I am really confused where to find the x1 filter capacitor
>

“X1” is a capacitor type designation, not a value. It means that the
capacitor is certified for direct connection across the AC line. They are
typically polypropylene dielectric capacitors which are “self-healing” in
the event of breakdown caused by voltage spikes well in excess of their
voltage rating.

You are looking for a capacitor in the 0.1 to 1.0 uF range with a voltage
rating of, typically, 250 VAC. They are pretty widely available and are
inexpensive.

I often see them advertised by the surplus store Electronic Goldmine,
usually in lots of five or ten for a couple of dollars. They are also
available from any electronic parts supplier.

If you’re having trouble locating a supplier, Google “X1 capacitor” and you
should get lots of possibilities.

The exact capacitance value is not too important, since its only purpose is
to attenuate fast spikes coming from the line and filter noise generated by
the power supply going back to the line. Physical fit is the other
important consideration.

I expect you’ll not have much trouble finding a replacement. Best of luck!

[Mike Spangler]

The same thing happened to me last spring. The rectangular box in question probably says RIFA on it. I bought replacements from Ebay. Not all power supplies use the same value of capacitors though. So it's best to look first and then buy.

You shouldn't have to drill out anything to get the power supply open. Although one model had 10 screws holding the case together. Another used none, or maybe two. The cover was mostly snap together. I found three or four different models in my collection. And every RIFA in the set was cracked and bulging. There were some blue ones with a German sounding name that were also not so good, but the were in better shape than the RIFA versions.

Four screws to get the PS out of the case, 10 screws to get the cover off the PS, and then another four to get the circuit board out for repairs. It was an exercise in fasteners. The hardest part is the strain relief on the power cable to the logic board. Turn 90 degrees and wiggle.

[Michael J. Mahon]

My usual approach is to use pliers to carefully squeeze the small side of
the strain relief, compressing the wire bundle slightly, then slip the
small end through the hole in the case.

These plastic strain reliefs have been around for decades, and IIRC were
originated by Heyco.

They can be easily reinserted by putting the two parts together over the
wire bundle, carefully aligning them with the original “bump” in the wires,
then squeezing again, this time from the larger end, and pressing it into
the hole in the case until it snaps/locks.